FST3125MX-FS

Overview

The FST3125MX is a high-speed CMOS bus switch from the Fairchild FST series, organized as four independent 1:1 switches. It operates within a supply voltage range of 4 V to 5.5 V and features a maximum on-resistance of 20 Ω. The device provides minimal propagation delay of 0.25 ns at 50 pF load and supports a maximum low-level output current of 128 mA. Packaged in a 14-pin SOIC with dimensions of 8.75 x 4 x 1.5 mm, it functions across an operating temperature range of -40 °C to +85 °C.

Feature Summary

• Low on-resistance allows input connection to outputs without adding propagation delay or generating additional ground bounce noise.
• Control inputs are compatible with TTL levels for simplified interface logic.
• Features zero bounce operation in flow-through mode.

Applications

• High-speed data bus switching applications
• Portable battery-powered systems requiring low power consumption
• Consumer electronics utilizing TTL-compatible logic interfaces

Procurement Notes

Verify the specific suffix 'FS' against official manufacturer documentation, as standard datasheets typically list 'FST3125MX'. Confirm package type and electrical specifications match the required system constraints. Ensure compatibility with ON Semiconductor part numbering conventions following the Fairchild integration, which may involve underscore-to-dash changes in ordering codes.

Selection Notes

Select this component when low propagation delay and minimal ground bounce are critical for signal integrity. The 4-bit configuration suits parallel data buses. Verify that the 4 V minimum supply voltage aligns with the system's power rails. Consider the 20 Ω on-resistance impact on signal attenuation for long traces.

Part Context

The FST3125MX belongs to the FST (Fairchild Switch Technology) family, derived from proven technology used in products like the FST3384. It is manufactured by Fairchild Semiconductor, which has been integrated into ON Semiconductor. The device is designed to replace older bus switch technologies with improved speed and lower power characteristics.

Replacement Considerations

The FST3125M is a direct equivalent in the same package. The FSTU3125M offers similar functionality but includes undershoot protection down to -2V. Check for updated part numbers using dashes instead of underscores per ON Semiconductor naming conventions.